I intended to write about Fresnelized TIRs for a while…
A simple TIR lens guides light on 2 paths:
The light emitted forward is refracted as it enters the lens and again as it leaves it.
The light emitted sideways is refracted, TIR-reflected and refracted again.
It is possible to fold one or more surfaces to reduce height. Some call this TIR-R, some Fresnel-TIRs.
Louie, not sure if that’s interesting for you but there’s also Ledil Stella - a silicone lens family for 30 mm LES. Over 30 mm I also see only reflectors.
Interesting diffuser in a small Verbatim bulb. This sits on a small Cree CXA COB. Old & inefficient (65lm/W), but it was only 1.40 so I bought it.
I’ll have to take pictures but it’s a very nice and even “beam”. Now if there’s a way to fit something like this on top of a 1” flashlight…
This is one of the biggest TIRs, 75mm
It’s only been tested with COBs up to 23mm but the LED opening seems much bigger than that.
Only problem is that when using a TIR with a large LES LED then the angle of incidence varies a lot, which may cause light leakage since total internal reflection only works at large incidence angles.
There’s one zoomie construction that I haven’t seen on a flashlight yet but found 3 lens makers that do it:
Moving lenslet array based.
Near the LED there’s a fixed TIR. The TIR has a lenslet array at the front face.
In front of the TIR there’s another lens. Its back is the exact negative of the TIR’s lenslet array; the front may be flat or refract the light in other ways.
When both lenses are very close (pretty much touching each other) - the lenslet array doesn’t do much, it’s almost like a regular TIR.
When they move out - the beam gets wider.
Pros:
fair efficiency, TIR capctures all the LED light
no need to put LED on a pole
easy to do fair waterproofing: seal at the TIR. Beam will be bad under water but submersion won’t cause damage.
short zooming movement
Cons:
current implementations don’t have AR coating which hurts efficiency
The description states PC with aluminum coating… I can only postulate that the center is not coated; helping to effect the large beam angle. And it’s a HUGE angle…